Converted flat: A flat resulting from the conversion of a house or former non-residential building. Includes buildings converted into a flat plus commercial premises (such as corner shops).

Purpose built flat, low rise: A flat in a purpose built block less than six storeys high. Includes cases where there is only one flat with independent access in a building which is also used for non-domestic purposes.

Purpose built flat, high rise: A flat in a purpose built block of at least six storeys high.